So called “solid ink” printers encompass various imaging devices, including printers and multi-function platforms and offer many advantages over many other types of high speed or high output document reproduction technologies such as laser and aqueous inkjet approaches. These often include higher document throughput (i.e., the number of documents reproduced over a unit of time), fewer mechanical components needed in the actual image transfer process, fewer consumables to replace, sharper images, as well as being more environmentally friendly (far less packaging waste).
A schematic diagram for a typical solid ink imaging device is illustrated in FIG. 1. The solid ink imaging device, hereafter simply referred to as a printer 100 has an ink loader 110 which receives and stages solid ink sticks which remain in solid form at room temperatures. The ink stock can be refilled by a user by simply adding more ink as needed to the ink loader 110. Separate loader channels are used for the different colors. For, example, only black solid ink is needed for monochrome printing, while solid ink colors of black, cyan, yellow and magenta are typically needed for color printing. Each color is loaded and fed in independent channels of the ink loader.
An ink melt unit 120 melts the ink by raising the temperature of the ink sufficiently above its melting point. During a melting phase of operation, the leading end of an ink stick contacts a melt plate or heated surface of the melt unit and the ink is melted in that region. The liquefied ink is supplied to a single or group of print heads 130 by gravity, pump action, or both. In accordance with the image to be reproduced, and under the control of a printer controller (not shown), a rotating print drum 140 receives ink droplets representing the image pixels to be transferred to paper or other media 170 from a sheet feeder 160. To facilitate the image transfer process, a pressure roller 150 presses the media 170 against the print drum 140, whereby the ink is transferred from the print drum to the media. The temperature of the ink can be carefully regulated so that the ink fully solidifies just after the image transfer.
While there may be advantages to the use of solid ink printers compared to other image reproduction technologies, high speed and voluminous printing sometimes creates problems not satisfactorily addressed by the prior art solid ink printing architectures. To meet the large ink volume requirement, ink loaders must have large storage capacity and be able to be replenished by loading ink at any time the loader has capacity for additional ink.
In typical prior art solid ink loaders, the ink sticks are positioned end to end in a channel or chute with a melt device on one end and a spring biased push block on the other end. This configuration requires the operator to manually advance the ink in the chute to provide space to insert additional ink sticks, to the extent there is capacity in the channel. This configuration may be somewhat cumbersome for loading large quantities of ink sticks in newer, larger capacity and faster printing products, as the operator has to repeatedly insert an ink stick and then push it forward manually when loading multiple ink sticks in the same channel.
Another issue is that the spring biased push block mechanism limits the amount of ink that can be stored in each channel. Extended capacity loaders with greater length require longer, higher force springs so the push block mechanism can become prohibitably bulky and expensive. Closing an access cover in opposition to the greater spring force needed for larger amounts of ink can be inconvenient or unacceptable to the user during the ink loading process.
Further, constant force springs limit the quantity of ink sticks that may be placed in the chute as the spring biased push block takes space in the chute that otherwise would hold additional ink.
Also, the spring biased push block pushes the ink from the back of the ink sticks, which may lead to undesirable steering or reorienting of the ink. Pushing larger sticks, particularly a longer stack of ink sticks from the back of a stick can lead to buckling and jamming of the sticks. Jamming is more pronounced when there is high feed friction. To minimize friction, a lubricious tape or similar non-stick surface is often used, adding additional cost to the product.